He took photos of the large animal and sent them to the Center of Coastal Studies in Provincetown. Researchers there determined that the creature was a thresher shark.

The Atlantic White Shark Conservancy said it visited that thresher shark Wednesday and another, similar one that had washed up dead on the Cape. They were working with the Massachusetts Division of Marine Fisheries and the National Oceanic and Atmospheric Administration’s Fisheries Service.

Both thresher sharks were male and likely stranded due to cold shock, the conservancy wrote in a Facebook post. The sharks were dissected and researchers took organ and tissue samples for further study.